There is
actually some anecdotal information from ancient times about how they stocked
carp and goldfish. From this graph it appears that fish introductions
actually peaked worldwide in the 1960s. Either they ran out of new species to
stock or they were happy with what they have. Recent introductions mostly for
a human food source now seem to be a lot of clams, mussels, and crustaceans
such as shrimp and crayfish.